The type of drive unit for transport trolley with which this invention is concerned employs a driving chain formed by alternately linking a center link having an elongated annular profile, with top and bottom links attached to both ends of the center link with connecting pins. A plate shape spacer intervenes between vertical portions which penetrate the center link of both trolley units, and couplings link all of these three with each other.
The transport equipment which utilizes this kind of drive unit can be classified into two broad categories: the overhead conveyor type in which the travel route of the chain supporting trolley is located above the travel route of the transport trolley, and the floor conveyor type in which the travel route of the transport trolley is located above the travel route of the chain supporting trolley. In the overhead type of conveyor transport equipment the drive chains are hung from a chain supporting trolley. A pusher is used for the bottom side link at appropriate intervals. A chain supporting trolley is generally linked to each of the center links positioned with the pusher. A driven dog of the transport trolley is pushed by the pusher and an antirunaway piece is installed close after the pusher. This antirunaway piece is vertically rockably pivoted to enable passing of the pusher thereover. In the floor type of conveyor transport equipment, it is common to install the pusher so that it protrudes upwardly from the lower disposed drive chains or the chain supporting trolley, and the driven dog and the antirunaway piece are installed similarly to close of the overhead type conveyor but to the lower side of the transport trolley.
In the transport trolley drive unit of the above-mentioned configuration, a vertical connecting pin connects the center link of the driving chain with the top and bottom links. The vertical pin penetrates the elongated annular center link to be longitudinally rockable, causing the chain supporting trolley installed to the center link and top and bottom links located on both the front and the rear to approach each other horizontally and the opposite surfaces to collide with each other. Because these chain supporting trolleys and the links are made of metal, collision of the two results in a loud metallic noise.
The other surface of the antirunaway piece is stricken by the pusher right before the pusher impacts against, and starts to push, the driven dog. Upon contact with the pusher the antirunaway piece tilts allowing the pusher to pass thereover and then the antirunaway piece falls backward returning to its normal position. When the pusher impacts against the antirunaway piece a loud metallic noise is generated.
After the antirunaway piece is tilted forwardly by the pusher the antirunaway piece recovers its original position but then the contacted surface of the antirunaway piece collides against a tilt stopper surface on the side in which the antirunaway piece is pivoted. This results in another loud metallic noise that is similar to the noise when the pusher collides against the driven dog.
These loud metallic changing and screeching noises are very disturbing and substantially degrade working conditions in the area.